1. Field of the Invention
The instant invention relates to flow control valves and more particularly to such valves in which fluid flows radially inwardly between a pair of seat surfaces and into an orifice communicating with one of the seat surfaces.
2. Description of the Related Art
Valves in which fluid flows radially inwardly between a pair of opposing circular seat surfaces are known in the art. For example, U.S. Pat. No. 3,856,043 to Feild et al pressure responsive fluid valve assembly in which such flow occurs. In Feild et al., the opposing valve seats are mounted on a pair of opposing valve members, the first of which is fixed relative to valve body and the second of which is spring-biased toward the first. Fluid is provided to the outer peripheries of the working faces and flows radially inwardly therebetween and into a bore formed in the second valve member and communicating with the second valve member working face.
The valve assembly of Feild et al. accurately regulates pressure over a wide range of relatively low flow rates. However, at higher flow rates, side thrust on the movable (second) valve member, as noted in the patent, prevents accurate regulation.
Also noted in the patent, the pressure distribution between the working faces decreases on an exponential basis from the radially outer peripheries of the working faces toward the orifice which is centered on the second valve member. This aspect of the disclosed Field et al. valve assembly is not necessarily disadvantageous in connection with the structure and operation of the device shown in the patent; however, it has been found to be very disadvantageous in valves which utilize opposed working faces wherein one of the working faces is mounted on a pressure-balanced piston, for example, in a pressure regulating, pressure relief or pressure reducing valve. When the working faces in such valves operate substantially apart from one another, such a pressure-balanced valve does not experience problems; however, as the working faces approach one another, the pressure between the faces drops thus causing the valve to slam shut rather than continuing its pressure regulation, relief or reducing function.